[coreboot] SeaBIOS and the Geode LX framebuffer

Stephen Crocker scrocker at ampltd.com
Mon Oct 6 17:55:19 CEST 2008

Jordan Crouse wrote:
> On 06/10/08 16:24 +0100, Stephen Crocker wrote:
>> Jordan Crouse wrote:
>>> On 06/10/08 15:31 +0100, Stephen Crocker wrote:
>>>> Carl-Daniel Hailfinger wrote:
>>>>> On 03.10.2008 12:29, Stephen Crocker wrote:
>>>>>> Is there a way of getting VGA support with SeaBIOS on the AMD Geode LX
>>>>>> framebuffer?  I have successfully built and tested a BIOS image that
>>>>>> appears to boot into DOS but the lack of display means that it is of
>>>>>> little use.  Is there a VGA ROM image that I can include?
>>>>> You'd need a VGA emulation VSA and AFAIK that piece of software is not
>>>>> available as open source due to an interesting rights situation.
>>>> How much of this is handled in AMD's binary VSA module?  I have been 
>>>> looking through both the AMD and OpenVSA source and it looks as if the 
>>>> lxvg module is supposed to handle VGA SMIs but I cannot find where this 
>>>> is actually done.
>>> None of it - the VGA is actually a seperate component under difference
>>> licensing.  Thats why you don't see it in the VSA code.
>> This is quite an important point, as a lot of programs access the I/O 
>> ports and framebuffer directly.  A VGA BIOS would be able to handle the 
>> functions provided by INT 10 but in my experience, that would not be 
>> enough.
> Not sure what you are trying to say here - beyond the PCI emulation, the
> VSA neither grants nor restricts access to the graphics hardware.  This
> is why we have been able to get away without VGA up to this point - both
> the libpayload driver and the kernel framebuffer drivers are perfectly
> good replacements for standard int 10 behavior.

I was under the impression that the Geode display hardware does not 
provide the standard I/O ports and memory areas exposed by standard VGA 
hardware (eg. ports 3d4/3d5 and segment A000) and that this was all 
emulated in the VSA using SMIs.  Am I incorrect about this?

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